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<div class="titlepage"><div><div><h4 class="title">
<a name="phoenix.modules.core.values"></a><a class="link" href="values.html" title="Values">Values</a>
</h4></div></div></div>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">phoenix</span><span class="special">/</span><span class="identifier">core</span><span class="special">/</span><span class="identifier">value</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<p>
          Whenever we see a constant in a partially applied function, an
        </p>
<pre class="programlisting"><span class="identifier">expression</span><span class="special">::</span><span class="identifier">value</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span>
</pre>
<p>
          (where T is the type of the constant) is automatically created for us.
          For instance:
        </p>
<pre class="programlisting"><span class="identifier">add</span><span class="special">(</span><span class="identifier">arg1</span><span class="special">,</span> <span class="number">6</span><span class="special">)</span>
</pre>
<p>
          Passing a second argument, <code class="computeroutput"><span class="number">6</span></code>,
          an <code class="computeroutput"><span class="identifier">expression</span><span class="special">::</span><span class="identifier">value</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is implicitly created behind the
          scenes. This is also equivalent to <code class="computeroutput"><span class="identifier">add</span><span class="special">(</span><span class="identifier">arg1</span><span class="special">,</span> <span class="identifier">val</span><span class="special">(</span><span class="number">6</span><span class="special">))</span></code>.
        </p>
<pre class="programlisting"><span class="identifier">val</span><span class="special">(</span><span class="identifier">v</span><span class="special">)</span>
</pre>
<p>
          generates an <code class="computeroutput"><span class="identifier">expression</span><span class="special">::</span><span class="identifier">value</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
          where <code class="computeroutput"><span class="identifier">T</span></code> is the type of
          <code class="computeroutput"><span class="identifier">v</span></code>. In most cases, there's
          no need to explicitly use <code class="computeroutput"><span class="identifier">val</span></code>,
          but, as we'll see later on, there are situations where this is unavoidable.
        </p>
<h3>
<a name="phoenix.modules.core.values.h0"></a>
          <span><a name="phoenix.modules.core.values.evaluating_a_value"></a></span><a class="link" href="values.html#phoenix.modules.core.values.evaluating_a_value">Evaluating
          a Value</a>
        </h3>
<p>
          Like arguments, values are also actors. As such, values can be evaluated.
          Invoking a value gives the value's identity. Example:
        </p>
<pre class="programlisting"><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">val</span><span class="special">(</span><span class="number">3</span><span class="special">)()</span> <span class="special">&lt;&lt;</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"Hello World"</span><span class="special">)();</span>
</pre>
<p>
          prints out "3 Hello World".
        </p>
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